1. Field of the Invention
The present invention relates generally to a fluid reservoir for the purpose of reserving a liquid, such as brake oil, etc. for use in the hydraulic brake system of an automotive vehicle or the like.
2. Description of the Prior Art
The typical construction of a fluid reservoir for reserving the operating liquid such as brake oil, etc. generally known in art of the hydraulic brake system is such that there are provided a cap over the opening at the top end of the reservoir body and a diaphragm disposed in the inside of the cap in such a manner that the moisture, dust or the like is efficiently prevented from entering into the reservoir body by function of the diaphragm. Referring more specifically to such a typical construction of the reservoir, it is noted that the circumferential portion of the diaphragm is adapted to be secured rigidly in position by way of the cap, but with such construction of the diaphragm to be secured directly by using the cap member, it is inevitable that the circumferential portion of the diaphragm is likely to be twisted followingly with the turning motion of the cap, when so rotated. In the attempt to prevent such trend of twisting motion of the diaphragm from occurring, therefore, it is generally constructed that there is further provided a force ring around the circumferential portion of the diaphragm and a step formed on the inner circumferential surface of the cap for operative engagement with the force ring in such fashion that the diaphragm may be caused to be urged into resting position at its circumferential portion by slidingly securing the engagement step on the cap along the force ring of the diaphragm, accordingly.
With the employment of such force ring, it would naturally make a job intricate as it would require added procedures when installing and removing the cap for the reservoir, and also, there is a fear that it would occasionally be forgotten to put the force ring back to position for use.
In this respect, it has then been proposed that there is formed an annular groove in the lower face of the force ring, with which the circumferential portion of the diaphragm is formed to engage together so that these two members may be assembled as a unit, and that there are provided a plurality of projections in the outer circumferential surface of the force ring and also a spiral groove in the female threads formed in the inner circumferential surface of the cap in such a manner that the force ring may resiliently be deformed manually slightly in the radial way and then forced into threaded engagement with the spiral groove of the female threads of the cap so that it may freely rotate with respect to the cap, whereby these diaphragm and cap can now be handled as a unit in practice. (see the Japanese Utility Model Laid-Open Application No. 14,765/1981).
With such construction of the reservoir, however, as it is generally inevitable to have the force ring deformed manually slightly prior to installation onto the cap as mentioned above, and therefore, it would be very possible that the diaphragm run out of engagement at its circumferential portion with the spiral groove of the force ring, when so deformed manually, and then this would occasionally make an installation job of the reservoir inefficient, after all.